1. Field of the Invention
This invention relates in general to computer systems, and more specifically charging battery packs that power computer systems.
2. Description of the Related Art
Personal computer systems have attained widespread use. These personal computer systems now provide computing power to many segments of today's modern society. A personal computer system can usually be defined as a desktop, floor-standing, or portable microcomputer that includes a system unit having a system processor or central processing unit (CPU) with associated memory, a display panel, a keyboard, a hard disk storage device or other type of storage media such as a floppy disk drive or a compact disk read only memory (CD ROM) drive. These personal computer systems are information handling systems which are designed primarily to give independent computing power to a single user or group of users and are inexpensively priced for purchase by individuals or small businesses.
A portable computer is a self-contained personal computer designed to be easily moved to and operated in various locations. Portable computers are often referred to as laptop, notebook or subnotebook computers. To be portable, these computers are small, compact, and lightweight. The conventional portable computer comprises a base portion and a lid portion that pivotally opens from the base portion when the portable computer is in use. The lid portion contains a flat panel display such as a liquid crystal display (LCD) or other relatively small display.
Recently, portable computers have become popular alternatives to traditional desktop or floor standing computer systems. Portable computers are typically powered by rechargeable batteries or, in the alternative, by an Alternating Current (AC) adapter electrically connected to an AC outlet. Often it is desirable to operate a portable computer for lengthy periods of time at a location where AC power is unavailable, as for example, on an airplane or outdoors. In such cases, the computer must be powered solely by a battery pack.
Although portable computers are smaller than desktop computers, and despite efforts to decrease the power consumption of portable computers, portable computers still consume a fairly significant amount of power during use. Thus, the amount of time that a battery pack can power a computer is limited. Therefore, the battery pack in the portable computer must be charged every so often.
One solution to maximize the amount of time between rechargings is to provide a portable computer with two battery packs that each can power the portable computer. In such a dual battery system, only one of the battery packs is charged and discharged at any one time. One such dual battery system is described in the U.S. patent titled Dual Smart Battery Detection System for Portable Computers, filed May 6, 1997, U.S. Pat. No. 5,818,200.
When charging a lithium ion battery pack, a charger supplies very little current to charge a battery pack from approximately 80% of full charge to fully charged. Consequently, the amount of time to charge a battery pack from 80% to 100% of full charge takes about as much time as to charge a battery pack from no charge to 80% of full charge.
What is desired is a faster way to charge a dual battery pack system.